Degradation Characteristics Of Atrazine-Degrading Strain LY-1 And LY-2 And Their Bioremediation Ability To Contaminated Soil

Atrazine(2-chloro-4-ethylamino-6-isopropyl-amino-s-triazine)is widely used in many countries,and which has been used for more than 40 years.Because of its long half-life and high mobility in soil,atrazine and its derivatives have been detected in soils,surface and ground water.Atrazine has a stable structure and is not easily degraded.It has a great threat to the environment and human beings.In this study,by enrichment culture,LY-1 and LY-2 were isolated from the surface soil of maize field where atrazine had been used for many years.They could use atrazine as a sole nitrogen source to grow.According to their physiological and biochemical characteristics,together with the sequential analysis,LY-1 and LY-2 were identified as Arthrobacter sp.strain and Enterobacter sp.strain,respectively.LY-2 was the first reported Enterobacter sp.strain in detail that could degrade atrazine.The results of PCR test showed that LY-1 contained atrazine-degrading gene trzN and atzBC,and the results of sequence determination and comparison demonstrated that the nucleotide sequences of trzN and atzBC from Arthrobacter sp.LY-1 showed 98%,99%and 100%sequence similarity with those of Arthrobacter aurescens TC1.LY-2 contained atrazine-degrading gene atzABC,and the results of sequence determination and comparison demonstrated that the nucleotide sequences of atzABC from Enterobacter sp.LY-2 showed 99%,100%and 99%sequence similarity with those of Arthrobacter aurescens TC1 and Pseudomonas sp.ADP.LY-1and LY-2 could degrade atrazine to non-toxic cyanuric acid.The degradation rates of LY-1 and LY-2 for atrazine of 100 mg/L within 48 h were 99.5%and 98.7%,respectively.The suitable temperature ranges of LY-1 and LY-2 were 20-35°C and 25-35°C,respectively.The suitable pH ranges were 6.0-10.0 and 6.0-9.0,respectively.The optimum temperature of LY-1 and LY-2 were30°C,and the optimum pH were 7.The optimum carbon sources were starch and sucrose,respectively.Additional nitrogen sources did not affect the degradation of atrazine.The ability of LY-1 and LY-2 repaired atrazine-contaminated soil were studied.The results showed that the effects of LY-1 and LY-2 on the degradation of atrazine in soil were closely related to the incubation time and inoculation amount.After incubation for 7 d at room temperature,70.9%and 60.4%of atrazine were removed by 1×10~6 CFU/mL of LY-1 and LY-2,respectively.After incubation for 14 d at room temperature,86.7%and 84.1%of atrazine were removed by 1×10~6 CFU/mL of LY-1 and LY-2,respectively.After incubation for 7 d at room temperature,90.6%and 78.9%of atrazine were removed by 1×10~8 CFU/mL of LY-1 and LY-2,respectively.After incubation for 14 d at room temperature,95.3%and 90.1%of atrazine were removed by 1×10~8 CFU/mL of LY-1 and LY-2,respectively.LY-1 and LY-2 showed good bioremediation effect in a relatively short period of time and had a better potential for bioremediation of atrazine-contaminated soil.